Field
Aspects of the present invention generally relate to power control of an information processing apparatus.
Description of the Related Art
Conventionally, in an auto document feeder (ADF) included in an image forming apparatus, a combination of a photointerrupter and a movable flag has been often used as a document detection unit for detecting that a document bundle is set on a document stacking tray. The movable flag blocks/transmits light from a light emitting unit of the photointerrupter, in accordance with the presence/absence of the document bundle. The document detection unit thus detects the presence/absence of the document bundle according to light received by a light receiving unit of the photointerrupter being turned ON and OFF.
Generally, an infrared light emitting diode (LED), requiring several hundred mW of power for light emission, is used as the light emitting unit of the photointerrupter. Thus, constant lighting of the infrared LED directly results in larger power consumption of the image forming apparatus. On the other hand, if the light emitting unit is turned OFF while the image forming apparatus is in a power saving mode to achieve low power consumption, the document detection unit would be unable to detect the document bundle.
Japanese Patent Application Laid-Open No. 2006-243238 discusses a technique for solving the problem. More specifically, the infrared LED serving as the light emitting unit of the photointerrupter is intermittently lit, and a document detection signal is monitored at the lighting timings, thereby reducing average power consumption of the infrared LED.
Unfortunately, in the conventional technique, a central processing unit (CPU) that controls lighting ON/OFF of the infrared LED and monitors a document detection signal needs to be in constant operation in order to perform the above-mentioned control/monitor. As a result, power consumption saving of the entire image forming apparatus is negatively affected.